The high optical quality imposed by LCD applications desires no large inclusions in the LCD glass substrate. It is known that precious metal inclusions are an issue where the glass melt is delivered, fined or formed using precious metal-containing equipment. As quality and surface requirements get more stringent, the size and quantity of allowable precious metal inclusions continue to decrease. The issue of precious metal inclusions in glass is not a new issue and is not unique to display glasses.
One postulated mechanism for the occurrence of precious metal inclusions in glass is the oxidation and subsequent dissociation and condensation of the precious metal at elevated temperatures. If these oxidation-condensation reactions occur in areas near free glass surfaces, the condensed metal can be incorporated in the glass and form a defect/inclusion. It was previously suggested that precious metal inclusions can be reduced by immersing the precious metal in an inert atmosphere, thus avoiding the oxidation and subsequent condensation of metal.
However, the introduction of an inert gas into the glass handling system is not easily done; it involves extra equipment that can be difficult to retrofit into existing glass production lines. Moreover, the inert gas atmosphere can be maintained only through a continuous flow of such protective gas, which can cause an undesired change of the thermal profile of the glass production line. Still further, even though this approach may be effective in reducing precious metal inclusions, it may not reduce contamination by other non-metal sources, such as SnO2, and the like.
Thus, there remains a need for a process and equipment which can effectively and efficiently abate the particles that can impact the quality of the glass in a glass-handling process. The present invention satisfies this need.